# Creating a circle section (Defense Mapping)

The Circle Section function creates a section of a circle, which could be used to represent a light sector or other polygon features.

There is only one coordinate that needs to be defined for this geometry, and it represents the start point on which the geodesic arc is based. It is from this point that the arc is created based on two azimuth values and a radius. By default, the arc is created in a clockwise direction. You can optionally configure the magnetic declination for the feature.

1. Start ArcMap.
2. On the menu bar, click Customize > Toolbars > Production Feature Builder.
3. Click the Feature Builder button on the Production Feature Builder toolbar.

The Feature Builder window appears.

提示:

The Feature Builder window can be placed anywhere in ArcMap, or in the Table Of Contents window, with the aid of the arrows showing the possible placement positions.

4. Choose Circle Section in the list on the Functions tab.

5. Define a coordinate for the start point of the polyline by doing one of the following:
• Clicking the Pinprick tool on the Production Feature Builder toolbar, then clicking on the map
• Typing the coordinates in the cells on the Input tab in the Coordinates area
提示:

To view the input coordinates on the map, double-click the row headers for each coordinate.

6. Click the cell next to From Azimuth and type the starting azimuth for the circle section in the cell.

This is the starting azimuth for the circle section. This angle defines the starting angle for the arc. Azimuth values are measured from north (0°). The default unit is degrees.

提示:

You can right-click the parameter name and change the unit of measurement. If you change the unit of measurement after defining a value, the value is converted to the new unit of measurement, and you may need to redefine the value.

7. Click the cell next to To Azimuth and type the ending azimuth for the circle section in the cell.

This is the ending azimuth for the circle section. This angle defines the ending angle for the arc. Azimuth values are measured from north (0°). The default unit is degrees.

提示:

You can right-click the parameter name and change the unit of measurement. If you change the unit of measurement after defining a value, the value is converted to the new unit of measurement, and you may need to redefine the value.

8. Click the cell next to Radius and type the distance for the radius in the cell.

This is the radius for the circle section, or the distance between the input coordinate and the arc. The default unit is Nautical Miles.

提示:

You can right-click the parameter name and change the unit of measurement. If you change the unit of measurement after defining a value, the value is converted to the new unit of measurement, and you may need to redefine the value.

9. If necessary, click the drop-down arrow next to Clockwise and choose False.

This indicates whether or not the arc is created in a clockwise direction. There are two options:

• True—The arc is created in a clockwise direction from the From Azimuth to the To Azimuth.
• False—The arc is created in a counterclockwise direction from the To Azimuth to the From Azimuth.
10. If necessary, click the cell next to MagVar Value and type a value for the magnetic variation.

This can be a specified value or from a field defined in the MagVar Source parameter. The default unit is degrees.

11. 提示:

You can right-click the parameter name and change the unit of measurement. If you change the unit of measurement after defining a value, the value is converted to the new unit of measurement, and you may need to redefine the value.

12. If necessary, click the drop-down arrow next to MagVar Source and choose a source for the magnetic variation.

This is the source of the magnetic variation value.

13. 提示:

You can right-click the parameter name and change the unit of measurement. If you change the unit of measurement after defining a value, the value is converted to the new unit of measurement, and you may need to redefine the value.

14. If necessary, click the drop-down arrow next to MagVar Year and choose a different year for the World Magnetic Model.

This is the year associated with the magnetic variation value.

注:

You can only choose a value for MagVar Year if Magnetic Model is selected for the MagVar Source property.

15. 提示:

You can right-click the parameter name and change the unit of measurement. If you change the unit of measurement after defining a value, the value is converted to the new unit of measurement, and you may need to redefine the value.

16. Click the Execute button .

A section of a circle surrounding a central point is created.

If the circle section does not appear, click the Add Scratch Data Layers button at the top of the Feature Builder window.

4/27/2014